I have seen quite a few frame failures. Some just from age/wear, some from crashing. The only spectacular failures I have seen were on two alluminum frames, A Giant, and a Cannondale. They both snapped off the headtube. I also caught on video tape a Ti frame snapping a headtube of during a race. There have been lots of mundane failures, just a crack propogating. Just this past friday I took a steel Performance bike out on a test ride and when I went off the curb the down tube snapped in two. To be honest I would not have noticed it(It just made it a little more springy and it had a cheap fork) except it suddenly shifted front and back when the frame spread.

So I would say, get what you like,treat it like you want, and don't worry about it to much. Worrying about a frame break, is like worring about getting struck by lightening. Just check the frame over every now and then.